Process for preparing periplogenia and intermediates secured therein



United States Patent ss 15 Claims. c1: 260-23955) The present invention relates to a process for preparing periplogenin, a naturally occurring cardioactive steroid, and to the new intermediates which are used in its preparation.

Periplogenin is the aglycone of periplocin and peri plocymarin and is found in those forms in certain kinds of St-rophanthus. Periplogenin has been described by Feigl [Biochem Zeitschr., vol. 2,. p. 404 (1907)] as being strongly cardioactive, with a similar kind of activity as that of the Strophanthus and the Digitalis glucosides. L. F. Fieser and M. Fieser, Steroids, Reinhold Publishing Corporation, New York, 1959', p. 803, list periplocymarin among the cardioactive derivatives of periplogenin with a high degree of activity.

The present invention affords a convenient and efficient process for the production of periplogenin, starting from a well-known and easily accessible starting material. Periplogenin may be represented by the following formula:

HO CH:

More specifically, desoxycorticosterone is converted to l4a-hydroXy-desoxycorticosterone as described by S. H. Eppstein et al. in I. Am. Chem. Soc. vol. 80, p. 3382 (1958). The latter compound is selectively acetylated in position 21 to yield 14a-hydroxy-desoxycorticosterone 21- acetate (1., R=CH CO) which is dehydrated to 14-dehydro-desoxycorticosterone acetate (II), also described by H. J. Ringold et al. in US. Patent 2,889,346 (June 2, 1959). The latter compound (II) is reduced with lithium aluminum hydride to yield 35,205,21 trihydroxy 4,14- pregnadiene (III) which is acetylated in the conventional manner to yield the corresponding 3[3,20,B,21-triacetate (IV, R=CH CO).

The elements of hypobromous acid are then added to the double bonds at C -C and C C of the latter compound, to yield the di-bromohydrin (V, R=CH CO), 4a, 14a-dibromo3B,5/i,155,2052l-pentahydroxypregnane 35, 20,8,2l-triacetate. Treatment of the latter di-bromohydrin with base eliminates the elements of hydrogen bromide and yields, with simultaneous hydrolysis of the ester groups, the di-epoxide (VI), 45,513,14,8,15/3-diepoxy-3;8,20,B,2l-trihydroXy-14-isopregnane. The vicinal hydroxyl groups at C and at C of the latter compound are then protected by means of acetonide formation, by treating compound (VI) with acetone and anhydrous copper sulfate, to obtain the corresponding acetonide, 4/3,5p,14;8,15;3-diepoxy- 3,8 hydroxy 20,8,21-isopropylidenedioxy-14-isopregnane (VII). Reductive opening of the epoxide rings of the latter compound, by treatment with lithium aluminum hydride, yields 35,5,6,l4B-trihydroxy-20p,-2l-isopropylidenedioxy-14-isopregnane (VIII). Conventional acetylation of compound (VIII), e.g. with acetic anhydride in pyridine, yields the corresponding 3,8-acetate (IX, R=CH CO).

Acid hydrolysis of the acetonide group of the compound (IX) yields the corresponding tetrol (X, R=CH CO), 3e acetoxy 5p,14B,20B,21-tetrahydroxy-14-isopregnane, which is, in turn, acetylated in the conventional manner to yield the corresponding 313,21--diacetoxy-5,8,145,20/8- trihydroxy-14-isopregnane (XI, R=CH CO).

Selective oxidation of the ZOB-hydroxy group of the latter compound 'with chromic oxide in dimethylformamide in the presence of sulfuric acid yields the corresponding 20-ketone (XII, R=CH CO), 3fi,2.1-diacetoxy-5B,145-dihydroxy-l4-isopregnane-20-one. The latter compound (XII) is reacted with lithium-ethoxyacetylene to obtain 3,8,21 diacetoxy-ZO-ethoxyethynyl-S/K,145,20B-trihydroxy- 14-isopregnane (XIII, R=CH CO).

Hydrolysis of the latter compound with alkali carbonate in lower alkanol yields a mixture of the corresponding pentahydroxy compound, 20-ethoxyethynyl-3 8,5 5,14,19,20/3, 2l-pentahydroxy-l4-isopregnane (XIV) and of 35,5 3,146, 20-tetrahydroxy-20(22)-dihydrocardenolide (XIVa). Mild mineral acid treatment of either compound (XIV) or compound (XIV-a) yields periplogenin (XVI). This mild acid treatment is preferably carrier out in a lower alkanol. Both hydrolysis of compound (XIII) and acid treatment of compound (XIV) or (XIVa) are carried out in liquid phase at a temperature up to about 30 C., preferably at room temperature.

Alternatively, the crude carbinol diacetate (XIII) may be rearranged under mild mineral acid conditions, preferably in a lower alkanol solvent, to yield the dihydroxydiacetate (XV, R=CH CO), which need not be isolated and can undergo hydrolysis and cyclization under the same conditions to yield peri-plogenin (XVI). Alternatively, compound (XV) can be transformed into periplogenin (XVI) by mild alkali treatment of alkali carbonate in lower alkanol. Rearrangement and acid hydrolysis of compound (XII) or alkaline hydrolysis of compound (XV) are carried out in liquid phase at a temperature up to about 30 C., preferably at room temperature.

In the present specification, including examples and claims, the expression room temperature, whenever it appears, is intended to mean a temperature between 20 and 25 C.

The following formulae and examples will illustrate this invention:

$112011 HO-CCEGOEIZ Example I A quantity of 20 g. of 14-dehydro-desoxycorticosterone acetate (Ringold, US. Pat. 2,889,346, issued June 2, 1959) in 100 cc. tetrahydrofuran was added dropwise to a suspension of 8 g. LiAlH in 300 cc. tetrahydrofuran. The suspension was stirred at room temperature for minutes and refluxed for an additional 20 minutes. Excess LiAlH was decomposed by addition of ethylacetate followed -by a saturated solution of Na2SO4 in water. The suspension was filtered and the product was isolated from the organic layer by evaporation of the solvent. It is 3B,20,8,21-trihydroxy-4,14-pregnadiene (III) M.P. 133- 136 C., [a] I-62.7 (1% in dioxane).

Conventional acetylation with 40 cc. acetic anhydride in cc. pyridine yields the triacetate (IV, R=CH CO), M.P. 129-130 C., [a] -I34 (1% in chloroform).

Example II To a quantity of the triacetate (IV) (15.4 g.) in 500 cc. dioxane there is added 16.5 g. of N-bromoacetamide followed by 3.3cc. of HCIO (70% aqueous) in 66 cc. water. The solution is kept at room temperature for two hours in the'dark and then poured into water. The resulting product is filtered, dried and crystallized from acetonehexane to give 4oc,14 dibrorno 3fi,5'{3,15;3,20fl,21 pentahydroxypregnane 35,205,21-triacetate (V, R=CH CO), M.P. 138-139 C. (dec.). [a] +73 (1% in chloroform).

Example 111 A quantity of 13.3 g. of the bis-bromohydrin (V) in 11 methanol was refluxed for one hour with 11.2 g. of KOH in 35 cc. water. The product was isolated with ether, washed with water and dried. Evaporation of the solvent aiforded 45,55, 145,155 diepoxy- 35,205,21-trihydroxy- 14-isopregnane (VI), M.P. 181-183 C., [a] 21.5 (1% in chloroform).

Example IV A quantity of 3.62 g. of the bis-epoxide (VI) was dissolved in 500 cc. acetone and stirred at room temperature with 7.2 g. anhydrous CuSO for 1.5 hours. Evaporation of the organic layer aiforded 45,55,145,155-diepoxy-35-hydroxy 205,21-isopropylidenedioxy-14-isopregnane (VII), M.P. 158-163 and 192-195 C., [a] +17.5 (1% in acetone).

Example V A quantity of 4.52 g. of the acetonide (VII) in 600 cc. tetrahydrofuran was added during minutes to a suspension of 6 g. LiAlH in 250 cc. tetrahydrofuran. After stirring for one hour at room temperature the suspension was refluxed for 4.5 hours. The usual work-up gave 35,55,145 trihydroxy 205,21 isopropylidenedioxy-14- isopregnane (VIII) M.P. 201203 C., [a] +33 (1% in acetone).

The corresponding 35-acetate was obtained with acetic anhydride in pyridine in the usual way, (IX, R=CH CO), M.P. 154-156 C., [a] -|46.4 (1% in chloroform).

Example VI A quantity of 3.69 g. of acetate (IX) dissolved in 150 cc. methanol was hydrolyzed with 150 cc. 0.05 N H 80 at room temperature for 16 hours. The product was isolated by extraction with methylenechloride. It is 35,55, 145,205,2l-pentahydroxy-l4-isopregnane-3 acetate (X), M.P. 207-209 C., [a] +29.9 1% in chloroform).

A quantity of this product (4.22 g.) dissolved in 60 m1. dioxane was acetylated with 2.26 cc. of acetic anhydride and 2.26 cc. pyridine at 5 C. for 16 hours and at 50 C. for 90 minutes. Usual work-up afforded 35,55,145, 205,21 pentahydroxy 14-iso-pregnane-35,2l-diacetate (XI, R=CH CO) M.P. 155-156 C., [a] +3O.9 C. (1% in chloroform).

Example VII To a quantity of 1.17 g. of the diacetate (XI), dissolved in cc. of dimethylformamide, there was added 1.2 g. chromic oxide followed by 20 cc. dimethylformamide containing 8 drops of concentrated H 80 After 16 hours at room temperature the mixture was extracted with CH Cl and the known 35,55,145,2l-tetrahydroxy- 14-isopregnan-20-one-3,2l-diacetate (XII, R=CH CO), was obtained. M.P. 150-151 C. (A. Lardon, Helv. 32, 1517 (1949) gives M.P. 148-151 C.) [a] +75 (1% in chloroform).

Example VIII A solution of ketone (XII), 105 mg. in 3 ml. benzene, was added to a suspension of lithium-ethoxyacetylene prepared from 35 mg. of lithium, 0.3 ml. bromobenzene and 0.4 cc. ethoxyacetylene in 11 cc. ether. Stirring was continued for one hour at 0 C. and for 2 hours at room temperature. 20-ethoxyethynyl-35,55,145,205,21-pentahydroxy-14-isopregnane-35,21-diacetate (XIII, R=CH CO) was isolated by extracting the mixture with CH Cl I.R. spectrum shows the characteristic acetylene band at 2250 cm.-

The crude carbinol diacetate (XIII) was hydrolyzed with mg. K CO in 5 ml. methanol at room temperature for 16 hours and at the reflux temperature for 15 minutes. A mixture of the corresponding pentahydroxy compound, 20 ethoxyethynyl-35,55,145,205,21-pentahydroxy-14-isopregnane (XIV) and of 35,55,145,20-tetrahydroxy-20(22)-dihydrocardenolide (XIVa) was obtained. This mixture was dissolved in 4 cc. methanol to which 1.5 cc. of 0.05 N H 80 solution was added. The solution was stirred at room temperature for one hour, then extracted with CH Cl to give a yellow oil from which the aglycone periplogenin was separated by chro matography. The LR. of authentic and synthetic periplogenin were super-imposable.

Alternatively the crude carbinol (XIII) was rearranged under mild acid conditions (0.05 N H 50 in methanol at room temperature for one hour) to give the ester (XV, R=CH CO), which was further hydrolyzed under mild acid (e.g. 0.05 N H 80 in methanol at room temperature) or alkaline (e.g. K CO in methanol at room temperature) conditions to give periplogenin (XVI).

I claim:

1. 35,205,21-trihydroxy-4,14 pregnadiene.

2. 4,14-pregnadiene-35,205-21-triacetate.

3. 4a, dibromo 35,55,155,205,21-pentahydroxypregnane-35,205,21-triacetate.

4. 45,55,145,15 diepoxy 35,205,21 trihydroxy-14- isopregnane.

5. 45,55,145,155 diepoxy 35 hydroxy 205,21- isopropylidenedioxy-14-isopregnane.

6. The process for preparing 35,55,145-trihydroxy-20 (22)-cardenolide which comprises subjecting 35,21-diacetoxy 20 ethoxy ethynyl-55,l45,205-trihydroxy-14-isopregnane to hydrolysis by treatment with an alkali carbonate in a lower alkanol in liquid phase at a temperature up to 30 C. to obtain a compound selected from a group consisting of 20-ethoxyethynyl-35,55,145,205,21- pentahydroxy 14 isopregnane and 35,55,145,20-tetrahydroxy-20(20) dihydro-cardenolide and mixtures thereof and treating the said compound thus obtained with a dilute mineral acid.

7. The process for preparing 35,55,145-trihydroxy-20 (22)-cardenolide which comprises rearranging 35,21-diacetoxy 20-ethoxy-ethynyl-55,145,205-trihydroxy-14-isopregnane by reacting said compound with a dilute mineral acid in liquid phase at a temperature up to 30 C. to yield 20-carbethoxymethylene-35,21-diacetoxy-55,145-dihydr0xy-14-isopregnane, and hydrolizing and cyclizing said latter compound by treating it, in liquid phase and in a lower alkanol, at a temperature up to 30 C., with a reagent selected from the group consisting of dilute mineral acids and alkali carbonates.

8. The process as claimed in claim 7, wherein said 20- carbethoxymethylene-35,21-diacetoxy-55,145 dihydroxy- 14-isopregnane is not isolated, but is hydrolyzed and cyclized by reacting with a dilute mineral acid.

9. The process as claimed in claim 6, wherein said mineral acid is selected from the group consisting of 0.05 N HCl and 0.05 N H 50 10. The process as claimed in claim 7, wherein said mineral acid is selected from the group consisting of 0.05 N HCl and 0.05 N H 80 11. The process as claimed in claim 6, wherein said alkali carbonate is potassium carbonate.

12. The process as claimed in claim 6, wherein said 35,21 diacetoxy 20 ethoxyethynyl-S/B,145,205-trihydroxy-14-isopregnane is obtained by treating 35,55,145- trihydroxy 205,21 -isopropylidenedioxy-I l-isopregnane 35-acetate with a mineral acid under mild conditions to obtain 35-acet-oxy-55,145,205,21-tetrahydroxy 14-isopregnane.

13. The process as claimed in claim 6, wherein said 35,21 diacetoxy 20 ethoxyethynyl-55,145,205-trihydroxy-14-isopregnane is obtained by treating said compound to obtain 35,2l-diacetoxy-S5,145,205-trihydroxy- 14-is0pregnane.

hydroxy-14-isopregnane is obtained by reacting said compounds with lithium-ethoxyacetylene.

No references cited.

LEWIS, GOTTS, Primary Examiner. ELBERT ROBERTS, Assistant Examiner. 

4. 4B,5B,14B,15 - DIEPOXY - 3B,20B,21 - TRIHYDROXY-14ISOPREGNANE.
 5. 4B,5B,14B,15B - DIEPOXY - 3B - HYDROXY - 20B,21ISOPROPYLIDENEDIOXY-14-ISOPREGNANE. 